Forest Investment Account

Abstract of TERP Project #0-23

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The effect of physiography and topography on fire regimes and forest communities

Author(s): Gray, Robert W.; Andrew, B.; Blackwell, Bruce Alan; Needoba, A.; Steele, F.
Imprint: [Victoria, B.C.] : R.W. Gray Consulting, 2002
Subject: Restoration Ecology, British Columbia, Forest Investment Account (FIA)
Series: Terrestrial Ecosystem Restoration Program Forest Investment Account (FIA) - Land Base Investment Program


Historical fire patterns, stand structures, and frequency of fire events were investigated for Natural Disturbance Type 3 (NDT3) and 4 (NDT4) forest stands. Plant associations are grouped into these Natural Disturbance Types based on historic disturbance regimes, and NDT3 ecosystem types are classified as being affected by relatively frequent stand-initiating fires. The current understanding is that these ecosystems contain even-aged stands progressing towards their climax condition, which are periodically returned to early seral stages as a result of fire. NDT4 ecosystems (ecosystems with frequent stand-maintaining fires) are the ones for which the most natural-disturbance research has been done, and a relatively good understanding has been gained regarding natural stand structures and fire frequencies. A knowledge gap existed for NDT3 ecosystems, especially regarding the influence of fires on stand structure based on elevation and aspect. This project investigated fire history and historic stand structure along an elevation and slope gradient, using transects that extended uphill from NDT4 ecosystems Companion transects were measured to collect stand structure and fire regime data along a similar elevation transect, but with a shift in aspect between the NDT4 ecosystem and the NDT3 ecosystem. Fire scar samples and species, age and site characteristics were inventoried at a series of sample points along the transects. Sampling took place in the Cranbrook, Invermere, Kamloops, Lillooet, and Squamish Forest Districts. The results of the analysis on south aspects suggests that frequent, mixed-severity fire regimes have influenced historic stand structure and ecosystem processes in biogeoclimatic subzones and variants currently considered to have experienced infrequent stand-replacement fire regimes. This is true for the MSdk in Cranbrook, MSdm1 in Invermere, MSxh in Kamloops and Lillooet, and the ESSFmw in Squamish. Additionally, significant inaccuracies were found in the mapped distribution of biogeoclimatic units in some forest districts. These identified discrepancies in fire regime classification and biogeoclimatic mapping can have significant consequences where the conservation of biodiversity is concerned. The current designation of many of these biogeoclimatic units as NDT3 warrants further investigation - fires appear to be of more mixed-severity as opposed to infrequent, high-severity. Results from this study may be useful in identifying future restoration sites and operational targets for biodiversity attributes. The data should also be useful in Landscape Unit Planning.
The project report is available from the Ministry library: Gray, R.W, B.A. Blackwell, A. Needoba, and F. Steele. 2002. The Effect of Physiography and Topography on Fire Regimes and Forest Communities. R.W. Gray Consulting & B.A. Blackwell & Associates Ltd. March 2002.
Project Name: Assessment of Historic Fire Regimes and Reference Stand Conditions, #0-23
Project Proponent: R.W. Gray Consulting Ltd.
Keywords: natural disturbance, historic fire regimes, NDT3, interior Douglas-fir

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Updated July 25, 2006 

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